Magnetic Modelling Methodology And Economical Research For Permanent-magnet-biased Saturation Based Fault Current Limiter

With fast development of power grid and rapid increase of electricity load, it has become an extremely urgent issue of limiting short circuit current to normal level in Chinese power system nowadays. As the continuous development of magnetic material and magnetic circuit topology, the fault current limiter based on permanent-magnet-biased saturation, namely PMFCL, is being considered to be an effective solution to suppress the fault current. With outstanding advantages such as in both economic and technological aspects, the PMFCLs is highly expected to find earlier applications in power systems.In order to develop high-voltage large-capacity applications for the fault current limiting technology based on permanent-magnet-biased saturation, the straight-line type PMFCL is chosen to carry out the theoretical exploration and technical research. The research contents cover several aspects as follows: a) Experimental research on stability of permanent magnet based on the straight-line type of PMFCL; b) Modelling methodology and experimental verification for the straight-line type of PMFCL; c) Economical research for large capacity applications of PMFCL.The stability of permanent magnet plays an important role in the operating principle of PMFCL. The experimental research on stability of permanent magnet for Nd-Fe-B N35which is now widely applied to PMFCLs was carried out according to the three aspects of time, temperature and external magnetic field. All of the work in Chapter2can be used to provide experimental basis for the application of Nd-Fe-B permanent magnet in straight-line type PMFCLs.Based on magnetic field analysis, the current limiting mechanism during the two stages is analyzed for the straight-line type PMFCL. On the base of calculating the overall leakage permeances, two corresponding equivalent magnetic circuit models were further established by taking into account of leakage flux effect. The simulation is carried out with MATLAB/SIMULINK as well as carrying out the experiment research, which proving the availability of the modelling methodology. All of the work in Chapter3can be used to provide analytical basis for the parameter design and optimization for PMFCL.For high-voltage power system above220kV, the economic advantage of Fault Current Limiters dominates the application value more comparing with the technological superiority. Based on TOC(Total Owning Cost) method, this dissertation builds the material and operating cost model of the PMFCL respectively, as well as the economic analysis model which determineded by the Inductance Summation, Inductance Ratio, Saturation Depth Ratio and other electromagnetic parameters. All of the work in Chapter4lays the foundation of the comprehensive optimization for the large capacity PMFCLThe research achievements of straight-line type PMFCL in the dissertation will further enrich the contents of the fault current limiting technology based on permanent-magnet-biased saturation, and present both theoretical significance and scientific value for the hogh-voltage and large-capacity PMFCL.